Method And Application Of Earthquake Response Analysis For Structure Containing A Tank Partially Filled With Water

A mass of water may exist in some structures in civil engineering, such as elevated water tower, aqueduct, pool, liquid storage tank and buildings with water tank. Under the base motion of the supporting structure subjected to earthquakes, structure containing a tank partially filled with water experiences motion in a certain dynamic response governed by the seismic excitation and its water reaction. Therefore, research on seismic response of this kind of structure relates to the interdisciplinary scopes consisted of seismic engineering and computational fluid dynamics.In practice, some approximate methods, in which all water is appended to structure or using some simplified models, are generally used to simulate the influence of water sloshing subjected to earthquake because water sloshing is complicated and difficult to be simulated accurately. However, many research results have shown that first method mentioned above is not suitable because it will magnify seismic inertia action, and the simplified models are only effective for ideal water sloshing in containers with regular and simple shape.Based on the practical engineering, the analytical method, numerical simulation and experimental research are carried out for solving several urgent problems about water sloshing and structural vibration in this dissertation. The main works are as follows:(1) The method using CFD commercial software is presented, which can simulate water sloshing exactly. It can take account of viscosity of water, turbulence of flow, large deformation of surface, and can model complicated shapes of container. Therefore, it is a suitable method for civil engineers to study water sloshing.(2) In this dissertation, aiming at structure containing a tank partially filled with water, two analysis models for dynamic responses under seismic excitations are presented, and their tanks are fixed rigidly on the floor or hanged under the floor, respectively. In these models, water sloshing is simulated by using FLUENT and vibration of structure by the C program which can execute in FLUENT. User defined functions (UDF) were employed to transfer the results of FLUENT to the C program.(3) The shaking table test for hanging tank has been carried out. The time history records of displacement and acceleration are obtained. The numerical simulative results are also obtained by use of the analysis model of hanging tank. According to the comparison, the numerical simulation and experimental results agree well. Then the numerical model can be verified.(4) Based on studying the relationship between forces to change the motion state of water and the same mass solid, the concept of equivalent mass of sloshing water is introduced. It is concluded that water inertia mass is a characteristic of changing water motion state. It is only relevant to shape of container and height of water, and irrelevant to the duration and value of forces. Experimental research and CFD results had proven that it is a reliable method to calculate the natural period of structure using equivalent mass of sloshing water instead of water mass when it consists of a tank. Based on the concept of equivalent mass of sloshing water, a simplified expression for calculating the main period of hanging tank was developed. The comparison shows good agreement of simplified expression with CFD's results.(5) Seismic responses of a deep ocean experimental pool with a movable base and an ellipsoidal elevated water tower were researched by using the analysis models which are presented in this dissertation, and the results showed that water sloshing had great influence to structure reaction under seismic excitations. In addition, some parameters influencing seismic responses of structure with water were discussed.(6) A novel tuned liquid dampers (TLD) rectangular tank with two angle-adjustable baffles is presented. Its natural period can be regularly changed in a wide range corresponding to the angles of the baffles. Its energy dissipation is relevant to the angles of the baffles and generally has more damp than traditional one. Theoretical and numerical results show that the novel TLD tank is much more effective in reducing the earthquake responses of structure than the same size general rectangular TLD tank. The reason of different effectiveness of TLD to reduce structure vibration under wind excitations and seismic excitations were studied.